在页面加载时将 json 文件读取为 javascript 变量

Question

I'm trying to read data from a json file into JavaScript so it can be used by other functions that are called when a user interacts with the page. I've tried, using jQuery and JS:

var products = null;
$.getJSON("products.json", function(data) {
  products = data;
  console.log(data);
});
console.log(products);

Which produces, as expected:

null
Array [ {…}, {…} ]

I understand this is because of the asynchronous nature of the jQuery code execution. I've read into it a bit, but I'm just struggling to wrap my head around how to re-structure my code (coming from pretty much exclusively Python).

This is how I'm seeing it:

var products = null;
$.getJSON("products.json", function(data) {
  products = data;
  console.log(data);
});

function do_stuff(){
  // Access the attributes of data and do stuff
}

function do_more_stuff(){
  // Do some more stuff with the data
}

I would probably have do_stuff() execute when the page body loads, and let's say do_more_stuff executes when the user selects something in a dropdown menu. Both need to access the data in products.json. I know there are many examples out there, but I'm just not getting it. How can I re-structure the code to actually work?

Answer 1

I believe you are looking for something like this:

function get_json(cb) {
    $.getJSON("products.json", function(data) {
      cb(data);
    });  
}

function cb(data) {
    // do stuff here if you want
    console.log(data)
}

get_json(cb)

Create a callback function cb (or call it do_stuff if you'd like). Pass a reference to that function to your async function (get_json). When the async operation is complete, call your callback function with the data you received.